program pascal;
var f,g:text;   t1,t2,t3,x,aux1,aux2,aux3:integer; sum,poz:int64; n,i:longint;
    a:array[0..100000] of longint;

  procedure citire;
  begin
  assign(f,'koba.in'); reset(f);
  assign(g,'koba.out'); rewrite(g);
  read(f,n,t1,t2,t3);
  t1:=t1 mod 10; t2:=t2 mod 10; t3:=t3 mod 10;
  aux1:=t1; aux2:=t2; aux3:=t3;
  close(f);
  end;

  procedure me;
  begin
  sum:=0;
  for i:=1 to n do
    begin
      x:=(t3+t2*t1) mod 10;
      sum:=sum+x;
      t1:=t2;
      t2:=t3;
      t3:=x;
    end;
  end;

begin
citire;
me;
write(g,sum);
close(g);
end.